Sealing method for cartons



L. BACK SEALIN'G METHOD FOR cARToNs Oct. 3, 1950 2 sheets-sheet 2 FiledJune 7, 1945 LEU/YARD BHCK INVEN TOR.

Patented Oct. 3, 1950 2,524,032 Y SEALING METHOD VFon cAR'roNs LeonardBack, Middletown, Ohio, assignor to The Interstate Folding Box CompanyApplication June 7, 1945, Serial No. 598,063 claims. (o1. 93-6) Myinvention relates to the problem of producing tight closures in seal endcartons. Seal end cartons are a well recognized type of foldingpaperboard box having a tubular body formed of body wallsin articulationWith each other and closure means consisting of ilaps articulated to theends of the body walls, Which ilaps are bent over inwardly, interfolded,and adhesively secured to form the closure, In the term tight closures Imean to include'closures ranging from those which are siftproof asrespects nely powdered contents to those which may be liquid or gastight and constitute hermetic seals.

The seal end carton has long presented a distinct problem in the cartonindustry. The usual commercial practice is to up-end the erected tubularcartons over a sealing mandrel, apply adhesive to the sealing flaps,interfold them accurately and then press them between the internalmandrel and an external pressure element. In this Way a reasonablysiftproof result may be obtained with accurately cut cartons, althoughfor many uses closures so formed are not as tight as they should be. Butthis method of sealing is capable of use only on the bottom closure of aseal end carton or on that carton closure which is made first, for thereason that in making the second or last closure after contents havebeen introduced into the cartons, an internal mandrel can no longer beused. The practice has been to fold a pair of ilaps inwardly Whileanother pair is outwardly folded, to apply adhesiveat least to theoutfolded aps, and then to fold these flaps inwardly successively. Thereis nothing, however, to supportthe ilaps from beneath .when they are infolded position. Thus, no effective pressure can be exerted on them fromwithout. The ilaps, particularly the innermostflaps, tend to curl orbecome depressed and 4hence to spring away from overlying flaps so thatno good adhesive bond can be obtained. As a consequence, the last formedseal end closure of a seal end carton is likely to be not only imperfectin physical construction but also perforate,` particularly at thecorners ofthe closure, so that such cartons are frequently found not tobe satisfactory carriers even for coarse grained granular materials.

Since a carton is no better than its poorest closure, those intended foruse with powders now employ, wherever cost will permit, either an innerliner or an outer wrap or both.

What is needed, as a first consideration is a procedure, applicable toboth ends of a seal endv carton, which will result in enforced physicalConformation of all aps in the closure so that an out using aconventional mandrel on either end.`

It is an object of my invention to provide means and a method which,while they can be carried' on without mechanism other than a simple toolhereinafter described, are nevertheless well adapted for .use inconnection with mechanical carton closing and sealing equipment.

It is also an object of my invention to provide means and a methodapplicable to the sealing of either or both ends of a seal end cartonirrespective of the position of the carton, so that the operation ofinverting the carton, hitherto generally used in carton sealing', may beeliminated with attendant economies in both time and equipment.

' These and other objects of my invention which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese specifications I accomplish by that mode of operation and `by thatmeans of which I shall now describe certain exemplary embodiments.

Reference is made to the accompanying drawings wherein:

Figure 1r is a partialplan View of an exemplary seal end carton.

-' and showing a means which I may use.

Figure '7 is a partial isometric view of the closed carton.

Figures 8, 9, 10 and 1l are isometric views showing successive stages inak modied mode of sealing a similar carton.

.Referring to Figure 1, I have shown an ordi- It is characteristic of myinvention, however,

that the sealing method and means hereinafter described and illustratedas applyinglto the seal.'

end closure shown in Figure 1 is similarly and even simultaneouslyapplicable to a sealendclosure on the other end of the carton blank.

From the form of the carton blank illustrated in Figure l, it will beapparent to one skilled in.

the art how the blank may be folded or tubed inl the ordinary way bybeing bent upon a pair of the score lines articulatingl the body wallsto each other, with the adhesiveattaclfinient` of the glue flap 5 to theouter edge of the body wall l. The size of the cartons, the number andYshape of"the.enclosing body walls and seal end flaps, and the specificcross sectional shape of the erected tubular structure do not constitutelimitations upon my inventionl and may be varied as desired". inaccordance withl known practices. For purposes of my invention I preferaccurately made and accurately cut'cartons having seal end flaps whichare also accurately cut and of as full asize asis consistent with goodcarton practice and board economy. Two at least of the napsconstitutingan opposedpair arepreferably of suificient size to extendYacross the entire'end of the erected carton.

In formingmy cartons I prefer to make the horizontal score lo" by meansof a continuous rule, the vertical scores and vertical outlinesbeingvmade by rules .butted against the first mentioned rule.Thisinsures that the cut lines demarkingthe seal end flaps from eachother donot extend into the area of the score by which, these flaps arearticulated to the respectivebodywalls. Otherwise, my, seal end cartonsmay be the Same as any commercial seal end structure, and' maybe printed.or not, as desired. In order tol make the tightest possible closures,even iorsiftproofing, I prefer to impose. upon thev board from which thecartons are. made areas of thermoplastic adhesive soplacedthatin thefinished carton the seal end flaps, the score lines by which theyy arearticulated to the body walls, and adjacent'areas of the body wallsthemselves are continuously coated with the adhesive substanceY asindicated at Il in'Fig. 1.

.W here the cartons are to hold liquids, the board should `be Vtreatedsoa-s to be impervious' to the liquids and so as to have its capillaritydestroyed, as in the copending application of Samuel Bergstein entitledLiquid Tight Seal End Cartons, Serial No. 600,754, filed June 2l,` 1945.One .eX- emp1arywayof doingthis is to impose uponone side of the board aproong substance which'V is drivenintotheboard to theextent ofsaturating itthrough or nearly throughto. theother side,

after which on the other side a continuous coating. of v thermoplasticproofing and. adhesive` substance is applied. However, where liquidtightness .is nota necessity, I may -make my cartons of untreated-board.Y

My procedure is based upon a concept oiinter folding` and.adhesivelysecuring ataleast` a pair 0f opposed caps in a seal end cartonwhile these flaps are supported from within by a thin but sufficientlystiiT metal plate, having a mounting portion extending outside thecarton at the same end. The plate operates to keep all the naps (sointerfolded) in accurate over-all face-to-face contact until theadhesive bond has sufficiently formed. It prevents any of the ilaps fromspringing or curling away from others and serves as an'inner pressureelement against which interoldedflaps may be compressed by means of anouter pressure element. It is manipulated and may be inserted andWithdrawn from the end of the carton uponwhich the interfolding andsealing operation is being performed. It does not employ anymeans suchas a mandrel inserted into the carton from the other end. Consequently,it'may be used on either end of the carton, and in particular may beemployed for forming the last closure on cartons which have alread;7been filled.

The rstessential is the bringing about of complete conformity and goodadhesion between the initially folded flaps; but when at least twoopposite ilaps have been so folded and secured, they form, ashereinafter more fully explained, a platform or bridge extending acrossthe carton onto which another ldap or flaps may be folded and adhesivelysecured, the platform at this time furnishing suiiicient support for thelast folded flap or flaps so that external pressure means can bring thelast folded iiaps into complete conformity and adhesive union with thefirst folded flaps.

Referring to Figure 2, when the carton has been erected, I place acrossthe open end of it a thin but relatively stiff metal or other plate l2,the seal end flaps having been folded sulficiently out of the way. Theplate may be moved and positioned entirely by hand, if desired, but itis also` readily susceptible of mechanical operation. I have shown itmounted upon a rod or shaft IS-which may be regarded either as a handlefor manual operation or as a means for mounting the plate l2'uponmechanical agencies to move it.

The plate l2, being widerthan the carton in oneI dimension, will overliea seal end fiap such as the flap 9; so that the iiap 9 must be bentoutwardly and downwardly sufficient to permit the positioning of theplate. The manner in which the plate is moved into position is not alimitation on the invention. It may be broughty in from the side by asliding motion transverse to the outfoldedflap 9. It may simply belowered into position. Itmay be brought into position by a' downward andinward movement. It may be located at a fixed station in a cartonsealing` The rst vsealing operation aiter'the positioning of the platemay be the inward folding vof flaps and 8, as shown in Figure 3. Thedimensions of. the plate are such that it extends across Vthe end of thecarton and .therebeyond in one direction at least as indicated. When.the iiaps 6A and.` 8 have been folded as shown, adhesive may be appliedto them and/or to the outwardly folded flap 'I by means in*v currentuse-on. carton sealing machines. 1f, as I prefer, the carton has`already been provided with an area I I of thermoplastic adhesive, thisadhesive is reactivated, as may be done by applying radiant heat to flap'I prior to its folding.

The flap I may then be folded over as shown in'Figure 4, coveringr flaps6 and 8.- Pressure to cause the flaps to conform with each other maythen be exerted by an external pressure means I4 (Figure 5). The plateI2 insures an accurate folding of the flaps 6, 8 and 'I holds the flapstogether when interfolded by clamping them between itself and theexternal member I4. Under the action of the external pressure means I4,the inner end of the plate can depress slightly, as shown in Figure 5,permitting tight closure to be made at the corners A and B of thecarton; but

the clamping pressure will be'sufliciently positive to enforce surfaceconformity of the flaps throughout their area.

Where the carton has been precoated with the adhesive I I the cornersare sealed by the flow of the softened adhesive. This is of the greatestimportance in producing closures which are completely and hermeticallytight. It is to be pointed out, however, that the accurate folding andinward support of the carton flaps insures their complete surfaceconformity and accurate adhesive union, and even with adhesive appliedin the ordinary way at the time of closure producesY a result superiorto results hitherto obtained, where internal mandrels could not be used,as for example, onV the top closure of a carto Where adhesive is appliedat the ltime of closure, I may use the means and method of BergsteinPatent 1,976,980, dated October 16, 1934, resulting in the depositing ofextra quantities of adhesive adjacent the corners of the flaps.

I have encountered no problem of adhesion of carton parts to thesupporting plate. When adhesive is applied to flap 'l during the processof effecting closure, it will be understood that the flaps 6 and 8, ifthey meet, overlie the plate completely and protect it from contact withthe adhesive. In cartons of certain shapes, as for example a cartonwhich is quite wide in relation to its depth, the inner, first foldedflaps will not meet unless extra board is used to make them longer.gether, and a heavy application of hot melt or other adhesive is made toflap I, I may relieve my supporting plate in the space between the endsof the inner flaps, or even cut it away altogetherin this area, y

In the case of cartons which have been precoated with thermoplasticadhesive, as in my preferred practice, the under sides of flaps 6 and Bmay be coated on their under sides with adhesive. Also the score linesmay be covered as described. The application of heat to flap 1, byradiant or other means, softens the adhesive on this flap and along itsscore line and at the corners; but is quite easily so applied as not tosoften the adhesive on the other flaps. When flap 'I is folded over, theadhesive on it will be in a condition to adhere to the flaps beneath,and upon cooling to form a firm bond with them; but it does not followthat suicient heat is transmitted through these flaps to effect greatsoftening of the adhesive on their under sides. On the contrary, the

.adhesive upon flaps 6 and 8 is not much affected,

especially since the supporting plate and the pressure element arepreferably not in a heated v condition..

When the inner flaps do not come to- The amount of pressure on the flapsbetween ling means brought close to its upper surface, or

if the flap 9 has not'previously been treated with adhesive, it will nowbe Vcoated as by a suitable roll coating device.

When the flap 9 is folded over onto the rigid platform formed of flaps6, 'l and 8, it can be brought into accurate registry with them and madeto have complete surface conformation with them by external pressuremeans through the supporting effect of the platform.

It will be seen that the result is a seal or closure of seal end type inwhich all flaps'have complete and accurate surface conformation. None ofthe flaps spring, bend or twist away from others during the sealing andhence cannot fail to be adhered throughout to the other flaps. A

At the corners C and D'of the cartonfFigure 4), the act of infolding theflap 9 and drawing it over the platform compresses the board and forms atight closure at these corners also. The pre-applied thermoplasticadhesive at these points, in my preferred practice, again flows to llall interstices and providesV an hermetic clo- Sure.

I prefer also to employ an expedient taught in the copending applicationof Samuel Bergstein, Serial No. 586,970, filed April 6, 1945nowabandoned, and effect a slight inward bowing of the body wall 4 of thecarton adjacent the line of articulation of flap 9. This may beaccomplished by a finger or the like on means for holding the carton asillustrated in Figure 6 at 15. The result of bowing the wall 4 inwardlyis to provide a ledge at the score line of flap 9 upon which the edgeC-D of the platform will rest. Then when the flap 9 is folded inwardly,`the platform is not only supported at its otherwise free edge but theadhesive treated surface of flap 9 is drawn tightly over the said freeedge of the platform making a tight adhesive closure all along this edgeand inclusive of the corner portions C and D.

By the `means and mode of Yoperation hereinabove described, I havesucceeded in producing tight and siftproof closures on seal end cartonswithout the use of internal mandrels. Where the board of the cartons isprecoated with liquid proof thermoplastic adhesiveV as described,v theclosure itself becomes liquid tight. Where the board of the cartons hasalso been treated so as not to be softenable by liquids, a carton sosealed is capable of holding liquids for long periods of time and is ineffect hermetically sealed.

In Figures 8 to 11 inclusive, I have indicated a modified procedure. Athin metal strip or plate I6 is caused to extend over the open end ofthe carton. It should not be wider than the carton.

If the carton has not previously been treated with thermoplasticadhesive, a suitable adhesive (thermoplastic or solvent) may be appliedto either of flaps 'I and 9. In Figure 9 I have Shown the flap 'I foldedover onto the plate I6, and in Figure 10 the flap 9 infolded to overliethe flap 1.

lIfheftwo liaps are thus adheredtogether insaccu- 'rate' surfaceconformation -while supported by the V.plate 16. fAn-.eXternalcooperating pressure element may,of course, Vbe used. After the adhesivehas set, the plate i6 is withdrawn endwise.

VFlaps 'l and 9 in adhesive union form a platform extending across thecarton endV from side to side, and supported-by the carton side walls 4and .2.A With an application of adhesivel to flaps f6 and '1, if theyhave not -previcusly been coated, these fiapsare folded over onto theplatform. j ln doing this, l prefer to indent the end walls Al Vand -.3adjacent Ythe lines of articulation of'theirfaps as by fingers, oneofwhich is shown at llin Figure 11. The result is that the ends of afnamethe-platform are not only supported, but the ilaps 6 and -'are drawntightly over the edges of the platform, forminga Very-tight closure atthe corners. Thestiffness of the platform-supports flaps Gand 1 andenables an external pressure element to produce accuratesurfaceconformation. ben tween these flaps and the platform until the adhesivehas set.

Itwill .be clear from the teachings herein that my'means and modesofsealingare applicable to either-.or both ends ofa seal end cartonirrespective .of the position of the carton. Hence both ends ofthecarton .may be closed and sealed while the carton is Ain a singleorientation, and no up-ending of the carton .is necessary between.closure operations. I may, for. example, position .a carton vertically,close it on the bottom and .then close and seal it on the top,.allwithout turning it endfor end, .and withvorwithout moving it fromstation to station ina machine.

Modifications may be made in my invention without departing fromthezspirit of it. Having thus described my invention in certainexemplary embodiments, 4what I claim-as new and desire to securebyLetters Patent is:

1. The .method of producing uniform adhesion between and surfaceconformation of sealing flaps articulated to the end of a carton body,which method includes supporting a pair of initially infolded flaps overa relatively thin plate extending across the carton body Vat said endand extending beyond the carton body at one side thereof over anoutfolded flap, adhering at least one remaining flap to the previouslyinfolded flaps in superposed position thereon while all of saidflaps'are so supported, thereupon withdrawing said plate ovel1 saidoutfolded flap and from beneath said infolded flaps and `adhering thepreviously outfolded nap in superposed position over said previouslyadhered flaps.

2. A method ofsealing flaps atthe end of. a cartonbody,.which includesas separate stages of folding and adhesively securing, the folding in ofapair of opposite flaps and the adhering of another flap theretov whilesaid flaps are supported by a plate extending across the carton end andtherebeyond at one side, and located on the inner side'of the saidflaps, and when an adhesive bond has been secured, withdrawing the saidplate transversely of the carton end and folding inwardly andadhesivelysecuring another flap to said previously folded and adhesivelysecured flaps.

3. A method of sealing naps articulated to an end of a carton body,which includes positioning across the open end of a carton body aplatelike Ymember extending transversely of the carton body therebeyondat one side edge, folding inwardly over said plate a -pair of oppositesealing flaps, folding inwardly and securing to the first mentioned napanother flap, thereupon withdrawing said supporting plate transverselyyof the `carton end to provide across the end of theA carton asupporting structure formed `of .infolded Vflaps secured togethercomplete surface conformity, and thereafter folding in and adhesivelysecuring tosaidv-previously folded and secured aps anfother carton flapto complete the closure.

4. `A process of closing seal end cartons .which comprises interfoldingand adhesively securing some lbut `not all -of the sealend Vflaps-ofsuchcartons, -twoat least of said flaps beingattached to opposite cartonwalls, pressing said fla-ps so as to secure surface conformity against aplatelike member positioned Atransversely inwardly from the same end ofsaid'carton so as to lielbeneath said flaps, whereby to form ofsaid'adhesively secured flaps a platform extending across the end ofsaid carton, then transversely.withdrawing said plate-like member, andinterfolding and adhesivelysecuring the remainderof ysaid flaps, saidremainder being supported -by said vpreformed platform and pressedthereagainst sogas tor-be brought into surface conformity therewith.l

5.*A process of yclosing rectangular seal end cartons which comprisesinterfolding andfad-hesively securing :a pair of opposite .seal end-iiaps plus athird seal end Hap of such cartons, lpressing said flaps sovas to secure surface conformity against aplate-like memberpositionedfrom the same endof thesaid cartonsoas to lie inwardly .of said flapswith a portionprojecting Abeyond the carton in the direction of theremaining-'unfolded flap, whereby toform .of said adhesively `securedflaps a .platform extending across the-end of said car-ton, then:withdrawing-said .plate-like member from the carton in the ydirectionoi' said unfolded flap, andfoldingover and adhesively securing said lastmentioned flap, said ap being supported by said preformed platformandpressed .thereagainst so as to be .brought tinto sur-face Vconformitytherewith.

6. The process claimed in claim 5 .including the step of .applyingadhesive to certain at least of said. flaps after the .positioning of.said .plate-like Y -gether in this fashion until an'adhesive bond hasbeensecured whereby to formv of said adhesively securedflaps.a'platform-extending across theend of said carton, thenwithdrawing said'platerlilre member substantially the plane of thecarton end, applying adhesive to the remainder of said flaps and foldingthem while supporting them by and pressing them against said preformedplatform so. as to holdY them in surface `conformity therewith.

8. The'process claimed in claim 5 in vwhich the cartons vhave preformedcoatings of thermoplastic adhesive on the flaps thereof and in whichjust prior to interfolding the adhesive is'reactivated by heat on asufficient number of `lapsto produce the adhesive unions set forth.

` 9. A process of closing rectangular seal end cartons which comprisespositioning a thin. platelike member across an open end of said cartonso that it extends beyond said open end at two opposite sides and atleast partially overlies two opposite seal end flaps which are inoutfolded condition, folding inwardly and adhesively securing togetherthe remaining pair of opposite flaps while pressing them against saidplate-like member so as to secure surface conformity, whereby to form ofsaid adhesively secured flaps a platform extending across the end ofsaid carton, then withdrawing said plate-like member in an endwisedirection7 and then folding over onto said platform and adhesivelysecuring thereto said rst mentioned pair of opposite flaps, pressingsaid flaps against said platform as a support so as to secure surfaceconformity between said platform and said flaps.

10. A process of closing seal end cartons without inverting them, whichcomprises effecting closure on both ends by steps involving folding somebut not all of the seal end flaps of the cartons at each end overplate-like members positioned from the same ends of the carton inwardlyof the folded flaps, and adhesively securing said flaps so as to formplatforms extending across the ends of said carton, then withdrawingsaid plate-like members transversely and adhesively securing theremainder of said flaps to said preformed platforms and pressing themthereagainst.

LEONARD BACK.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,365,415 Lawrence Jan. 11, 19211,577,850 Peters et al Mar. 23, 1926 1,634,073 Labombarde June 28,19271,965,897 Jurgens et al July 10,1934 2,074,357 Bergstein Mar. 23, 19372,206,203 Richard July 2, 1940 2,217,757 Lindley Oct. l5, 1940 2,266,054Lowey et al Dec. 16, 1941 2,328,758 Vergobbi Sept. 7, 1943 2,330,466Bergstein Sept. 28, 1943 FOREIGN PATENTS Number Country Date 281,794Great Britain Dec. 15, 1927

